UCS Fabric Interconnect supports two types of switching modes: end-host mode (EHM) and the standard Ethernet switching mode. The default switching mode is the EHM, which eliminates the use of the Spanning Tree Protocol (STP) on Fabric Interconnect. The standard Ethernet switching is rarely used and it is recommended that you do not implement this option unless there is a use case.
Switching mode conversion is a disruptive change requiring a Fabric Interconnect reboot and hence should be planned during a scheduled maintenance window.